Numerous methods and apparatus for introducing liquid into containers exist in the prior art. Such methods and apparatus utilize various controls and measurements for determining when a desired amount of liquid has been introduced into the container. Included in such systems are photoelectric, volumetric, ultrasonic and weight measurements and controls. More recently in the paint industry, ultrasonic controls have been used to sense the level of the paint as it rises in the container and to initiate a signal to close the fill valve when a certain level has been reached. However, one of the problems with ultrasonic controls is that they are not sufficiently accurate to insure that a predetermined amount of paint is introduced in the container. Another problem is that ultrasonic controls are limited as to the range of measurement thereby increasing the time it takes to fill a container. In addition, some ultrasonic controls are relatively expensive and suffer other problems due to bubbling or frothing at the surface of the paint in the container; and the location of the sensor adjacent the fill valve atop the container.